During operation, wind energy installations are connected to the electrical grid of a wind farm. Wind farms are connected to the public supply grid. Both for the wind energy installation and for the wind farm, it is necessary to ensure that the electrical energy that is generated is fed into the respective grid in a form which is compatible with that grid. By way of example, the electrical energy is therefore fed into the grid at a specific frequency, at a specific voltage, and with a specific reactive power component.
The grid requirements are not constant. For example, the grid can demand that the maximum power be fed in at times in which it is subject to an increased load. When the voltages in the grid fall, the grid can additionally demand an increased reactive power component from the wind energy installation, in order to support the voltage.
The object of the control unit is to control the wind energy installation and the wind farm such that the electrical energy is provided in a manner which is compatible with the grid. In order to ensure that the control unit is provided with the information which it has to take into account for this task, control commands are issued. The control command represents a control variable for the control unit. The control variables are processed in the control unit, and the wind energy installation and the wind farm are controlled as a function of the control variables.
The communication directed at the control unit is organized differently on the grids of different operators. For example, the control commands for one operator may be transmitted in digital form, while the other operator uses analog control commands. For one operator, the nominal value of the reactive power may be defined as a percentage component of the total rating, while another operator transmits the corresponding control command as the phase angle φ between the current fed in and the grid voltage.
Until now, it has been normal practice to match the control units to the requirements of the respective operator and of the respective grid. However, this results in considerable complexity. For example, when producing a wind energy installation and when setting up a wind farm, it is first of all necessary to know the grid in which the wind energy installation or the wind farm will be used, before the control unit can be completed. A multiplicity of parallel versions of the control unit must be kept available and developed further for maintenance of existing wind energy installations and wind farms.